The anterolateral ligament - the safety belt for the cruciate ligament?

Failure rate for anterior cruciate ligament reconstruction high

The majority of athletes with anterior cruciate ligament (ACL) injuries opt for surgery with reconstruction of the ACL. Many achieve their original level of performance and can return to play without difficulty. However, approximately 20-25% of athletes with surgically repaired ACL suffer a re-injury with a new tear of the ACL or the ACL loses its strength and stability (anterior cruciate ligament insufficiency). The results of these failures are multifactorial, but a major one is the so-called anterolateral rotational instability, which may not have been restored or recognised during cruciate ligament reconstruction.

What happens in the knee joint after an ACL rupture?

Movement kinematic examinations show the changes in the knee joint after complete rupture of the anterior cruciate ligament:

After complete severing or tearing of the anterior cruciate ligament, an anterior knee joint instability occurs with increased forward force of the lower leg (anterior tibial translation). As a result of the existing anterior instability of the knee joint, there is a forward displacement (subluxation) of the lower leg (tibia) under load of the knee joint. In addition to anterior instability, an ACL rupture also causes so-called anterolateral rotational instability. This instability is characterised by a shift of the centre of rotation to the inner joint section. This increases the mobility of the outer lower leg (lateral tibial plateau) through an increased forward force and extended internal rotation.

Displacement of the rotation axis after ACL rupture

Centre of rotation of the knee joint with intact anterior cruciate ligament:

central axis of rotation

Centre of rotation of the knee joint in anterior cruciate ligament rupture:

Shift inwards

Animation - Change in the axis of rotation in anterior cruciate ligament rupture:

Central inwards

Based on source: Domnick et al. WJO 2016

Biomechanics of the intact anterior cruciate ligament

The main task of the ACL is both to stabilise against a forward force of the lower leg (anterior tibial translation (ATT) force) and to maintain rotational stability of the knee joint. These two stabilisation tasks can be investigated using the Lachman and pivot shift tests:

Lachman test

Pivot Shift Test

Anatomy and function of the knee joint

"Knee surgeons describe new ligament at knee joint".

In 2013, Dr Steven Claes , one of the two knee surgeons, described in his studies a fibrous ligament that can be injured when the anterior cruciate ligament is torn. Anatomically, the ligament or ligament complex runs on the outside of the knee joint and presumably several anatomical structures can be held responsible for it, including the iliotibial band complex , the anterolateral ligament and the Kaplan fibres. The essential function of the ligament is to maintain rotational stability, especially during internal rotation of the knee joint. Reconstruction of this ligament can successfully improve overall stability in patients with high-grade pivot shift phenomenon or in patients with persistent pivot shift after cruciate ligament reconstruction. The ligament often eludes visualisation in MRI findings, so that if there is a suspicion of this in the clinical examination (stability test), the indication for ACL reconstruction is made by the surgeon after compliance with specific criteria.

→ Find out more about "Combined knee instabilities (ALL)"

Our decision criteria

Guidelines for the treatment of anterolateral instability

They are based on the consensus paper of the Ligament Expert Group (consensus paper on the management of internal rotation and instability of the anterior cruciate ligament - deficient knee). Requirements for surgery of the anterolateral ligament complex (ALL) in reconstruction of the anterior cruciate ligament (ACL). According to the ALL Expert Group, at least one primary or two secondary criteria should be present.

Decision. primary criterion:

• Re-injury after ACL plastic
• pivot Shift Grade 2 and 3
• high level contact sports
• hyperlaxe, patients with weak connective tissue
• segond fracture

Secondary criterion:

• Cruciate ligament rupture of the other knee joint
• Lachman test greater than 10 mm (side comparison)
• Patient age less than 25 years